Missouri Gov. Jay Nixon said Tuesday that he is prepared to call out the National Guard again to quell any violent unrest that might result from the grand jury decision on whether to indict a police officer who shot teenager Michael Brown in August.

Missouri Gov. Jay Nixon emphasized what he called the "dual pillars of safety and speech" in a press conference Tuesday, where he and members of the law enforcement community outlined their plan to maintain order once a grand jury decision is announced in the Michael Brown killing.

"Violence will not be tolerated," Governor Nixon said.

Tensions in Ferguson and the surrounding region have been increasingly high in recent days as police, activists, and residents brace for the decision on whether to indict the police officer who shot and killed the unarmed teenager on Aug. 9. The prosecuting attorney has said it is likely to come in mid-to-late November.

Since the shooting on Aug. 9, there have been consistent – and, after the initial days following the shooting, largely peaceful – protests in the town of 21,000, but many are concerned that violence will again erupt after the decision, especially if the grand jury opts not to indict officer Darren Wilson.

Gun sales have been up across the region as residents worry about possible riots and prepare to protect themselves. In the weeks after Ferguson, there were concerns both about violence from some protesters as well as disproportionate response from police officers, many of whom wore riot gear, implemented mass arrests, and used tear gas and rubber bullets to quell protests.

At the press conference, Nixon and the members of the unified command said that those concerns had been heard, and emphasized the hours of work with activists and community members to find common ground and seek long-term solutions to the root causes of the Ferguson unrest – discussions they said they hoped would bear fruit in the coming weeks, whatever the response to the grand jury decision is.

"Our dual pillars here are safety and speech," Nixon said. "The vast majority of people who want to speak want to do so in a peaceful fashion."

But they also emphasized that safety is paramount and violence will not be tolerated. More than 1,000 officers have received specialized training in crowd control, Nixon said, including training on the constitutional rights of protesters. Officers will be brought in from around the state to provide support, additional equipment has been distributed, and the National Guard has been part of contingency planning. Nixon said he would call on them for backup if necessary.

"These measures are not being taken because we are convinced violence will occur, but because we have a responsibility to prepare for any contingency," Nixon said.

"Police officers recognize that peaceful protesters are exercising their right to free speech," added Sam Dotson, the police chief for metropolitan St. Louis. "But criminal actions, acts of violence, will not be tolerated."

In advance of the press conference, community activists expressed concerns about a potential repeat of harsh police tactics in dealing with protests, and emphasized the principles they believe need to be paramount for police. Those include minimal protection gear, no interruption of communication by interfering with cell or Internet access, respect for safe houses, no mass arrests, and no use of armored vehicles, tear gas, or other crowd-control equipment.

"Governor Nixon’s choice to act unilaterally in this police plan is a slap in the face to every protestor who has worked tirelessly over the past 90+ days to reach peaceful solutions,” said Taurean Russell, cofounder of handsupunited.org, in a statement.

The members of the unified command, which includes Chief Dotson along with St. Louis County Police Chief Jon Belmar and Missouri Highway Patrol Capt. Ron Johnson, said they were aware of protesters' concerns, and emphasized the importance of the discussions that have been taking place with community members, faith leaders, and activists in recent weeks and months.

"We’re prepared, but we’re engaged," said Chief Belmar, noting that he was planning to spend several hours Tuesday night in discussions with community members. He said officers would try to "portray a posture of appropriateness to the situation we’re faced with," but said that officers' safety also needs to be a concern, and that in some instances riot gear is necessary.

Nixon highlighted the commission being in place to establish root causes for and recommend solutions to the unrest that resulted in Ferguson, and expressed hopes for "long-term lasting movement forward on issues that have been intractable."

But when the grand jury decision comes down, he also emphasized that safety will be the ultimate priority.

"If folks cross that safety line on property or person, we will use full power of the law to keep peace," he said.